Merge dashpay#7027: ci: add caching for dependency sources in CI workflow

72eb33d fix: use RAII style cache save (pasta)
8b4b623 fix: use actions/cache/restore in build-depends.yml (pasta)
f3eb750 ci: add caching for dependency sources in CI workflow (pasta)

Pull request description:

  ## Issue being fixed or feature implemented
  - Introduced a new job `cache-sources` in the GitHub Actions workflow to cache dependency sources, improving build efficiency.
  - Updated existing jobs to depend on `cache-sources` to utilize cached data when available.
  - Created a new file `cache-depends-sources.yml` to define the caching logic, including steps for checking and downloading sources.

  This is more important because in DashCoreAutoGuix, because things are less often merged into develop (they are merged into their own feature branch) the shared caches coming from develop become stale and get evicted. If we run it daily, it will ensure the shared cache (in develop) can be used by the runs in the feature branches. It may also be useful here, because currently each run tries to generate it's own cache, and they may race, and the sources used by the different runs are slightly different.

  This is normally masked, because the final depends are cached well in this repo.

  This change enhances the CI process by reducing redundant downloads and speeding up builds.

  ## What was done?

  ## How Has This Been Tested?

  ## Breaking Changes

  ## Checklist:
    _Go over all the following points, and put an `x` in all the boxes that apply._
  - [ ] I have performed a self-review of my own code
  - [ ] I have commented my code, particularly in hard-to-understand areas
  - [ ] I have added or updated relevant unit/integration/functional/e2e tests
  - [ ] I have made corresponding changes to the documentation
  - [x] I have assigned this pull request to a milestone _(for repository code-owners and collaborators only)_

ACKs for top commit:
  UdjinM6:
    utACK 72eb33d
  kwvg:
    utACK 72eb33d

Tree-SHA512: 1f246340f86bd083515dd0ee2e8f6f515adc0f011d7d02c7b3507e4eb3e34314a997c827e13277b5ec76e01e37d8f1633b57a98b6a93b3d6a1d8e53d6b3b5f0a

Author: PastaPastaPasta

.github/workflows/build-depends.yml

@@ -44,8 +44,8 @@ jobs:
 
         shell: bash
 
-      - name: Cache depends sources
-        uses: actions/cache@v4
+      - name: Restore depends sources
+        uses: actions/cache/restore@v4
         with:
           path: |
             depends/sources

.github/workflows/build.yml

@@ -37,6 +37,12 @@ jobs:
             echo "skip=false" >> $GITHUB_OUTPUT
           fi
 
+  cache-sources:
+    name: Cache depends sources
+    needs: [check-skip]
+    if: ${{ needs.check-skip.outputs.skip == 'false' }}
+    uses: ./.github/workflows/cache-depends-sources.yml
+
   container:
     name: Build container
     needs: [check-skip]
@@ -60,7 +66,7 @@ jobs:
   depends-arm-linux:
     name: arm-linux-gnueabihf
     uses: ./.github/workflows/build-depends.yml
-    needs: [container]
+    needs: [container, cache-sources]
     if: ${{ vars.SKIP_ARM_LINUX == '' }}
     with:
       build-target: arm-linux
@@ -69,7 +75,7 @@ jobs:
   depends-linux64:
     name: x86_64-pc-linux-gnu
     uses: ./.github/workflows/build-depends.yml
-    needs: [container]
+    needs: [container, cache-sources]
     if: |
       vars.SKIP_LINUX64 == '' ||
       vars.SKIP_LINUX64_FUZZ == '' ||
@@ -82,7 +88,7 @@ jobs:
   depends-linux64_multiprocess:
     name: x86_64-pc-linux-gnu_multiprocess
     uses: ./.github/workflows/build-depends.yml
-    needs: [container]
+    needs: [container, cache-sources]
     if: |
       vars.SKIP_LINUX64_MULTIPROCESS == '' ||
       vars.SKIP_LINUX64_TSAN == ''
@@ -93,7 +99,7 @@ jobs:
   depends-linux64_nowallet:
     name: x86_64-pc-linux-gnu_nowallet
     uses: ./.github/workflows/build-depends.yml
-    needs: [container]
+    needs: [container, cache-sources]
     if: ${{ vars.SKIP_LINUX64_NOWALLET == '' }}
     with:
       build-target: linux64_nowallet
@@ -102,7 +108,7 @@ jobs:
   depends-mac:
     name: x86_64-apple-darwin
     uses: ./.github/workflows/build-depends.yml
-    needs: [container]
+    needs: [container, cache-sources]
     if: ${{ vars.SKIP_MAC == '' }}
     with:
       build-target: mac
@@ -111,7 +117,7 @@ jobs:
   depends-win64:
     name: x86_64-w64-mingw32
     uses: ./.github/workflows/build-depends.yml
-    needs: [container]
+    needs: [container, cache-sources]
     if: ${{ vars.SKIP_WIN64 == '' }}
     with:
       build-target: win64

.github/workflows/cache-depends-sources.yml

@@ -0,0 +1,30 @@
+name: Cache depends sources
+
+on:
+  workflow_call:
+  schedule:
+    # Run daily at 6 AM UTC on the default branch to keep cache warm
+    - cron: '0 6 * * *'
+
+jobs:
+  cache-sources:
+    name: Cache depends sources
+    runs-on: ubuntu-24.04-arm
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.pull_request.head.sha || github.sha }}
+
+      - name: Check for cached sources
+        id: cache-check
+        uses: actions/cache@v4
+        with:
+          path: depends/sources
+          key: depends-sources-${{ hashFiles('depends/packages/*') }}
+          restore-keys: depends-sources-
+          lookup-only: true
+
+      - name: Download sources
+        if: steps.cache-check.outputs.cache-hit != 'true'
+        run: make -C depends download